This invention relates to a process for preparing cyclic phosphites which are useful as stabilizers for polymer compositions.
One of the most commercially significant cyclic phosphites is bis(alkylphenyl)pentaerythritol diphosphite. This diphosphite can have either of the following structures, ##STR1## wherein each R is an independently selected alkyl group containing 3 to 12 carbon atoms. Both of these structures are contemporaneously produced by most bis(alkylphenyl)pentaerythritol diphosphite processes.
The structure (I) diphosphite is preferred while the structure (II) diphosphite is considered an impurity. It is preferred that no more than about 3 weight percent of the structure (II) diphosphite be present in a commercial product.
Many processes have been proposed for producing bis(alkylphenyl)pentaerythritol) diphosphite. See, for example, the several processes described in U.S. Pat. No(s). 4,305,866 and 4,665,211. Also see European Patent Application Nos. 0 143 464, 0 159 294, and 0 186 628, and United Kingdom patent No. 2046273B.
Most, if not all, of the processes feature long reaction times, severe reaction conditions, expensive reagents, low yields and/or a low product purity.